how to make clusters from small polygons with constraint of boundary touching?

Question

I want to make some clusters from a bunch of small polygons with the constraint that each basic unit (polygon) in the resultant cluster must share a portion of its boundary with at least one other basic unit (polygon) in the same cluster. This is becuase of the reason that i want the resultant clusters contagious.

Answer 1

Making use of feature layers, selections, and a while loop to select neighboring features until no new features are selected is the way to go, if you just want to cluster all features that touch together. The script below adds a field and updates it with a cluster number. The clusters represent all touching features.

import arcpy

#In feature class
fc = r"C:\Users\Emil\Documents\ArcGIS\Default.gdb\testpolygon"

#New cluster field name
fieldname = "Group"

#Add field
arcpy.AddField_management (fc, fieldname, "SHORT")

#Make feature layer to allow for selection
arcpy.MakeFeatureLayer_management (fc, "lyr")

#Get layer OID field name for use in SQL
OIDfieldName = arcpy.Describe ("lyr").OIDFieldName

#Create list for OIDs that have been selected
allselectedOIDs = []

#Variable to designate clusters
Cluster = 1

#cursor to iterate through features
cursor = arcpy.da.SearchCursor("lyr", "OID@")
for row in cursor:

    #Check if OID has been selected and assigned to a cluster
    if row[0] in allselectedOIDs:
        #skip iteration
        continue

    #SQL to select single feature
    sql = '"{0}" = {1}'.format (OIDfieldName, row[0])

    #Set old selection count to 0
    OldSelectionCount = 0

    #Select feature
    arcpy.SelectLayerByAttribute_management ("lyr", "", sql)

    #set new selection count to 1
    NewSelectionCount = 1

    #While loop 
    while NewSelectionCount != OldSelectionCount:

        #Update old selection count
        OldSelectionCount = NewSelectionCount

        #Select neighbors
        arcpy.SelectLayerByLocation_management ("lyr", "", "lyr")

        #Get new selection count
        NewSelectionCount = int(arcpy.GetCount_management("lyr").getOutput(0))

    #Get list of selected feature OIDs with list comprehension
    selectedOIDs = [r[0] for r in arcpy.da.SearchCursor("lyr", "OID@")]

    #Add selected feature OIDs to all OIDs list
    allselectedOIDs += selectedOIDs 

    #Update layer field with cluster number
    arcpy.CalculateField_management ("lyr", fieldname, Cluster)

    print Cluster
    #Add 1 to cluster variable
    Cluster += 1

#Clean up
del row
del cursor

Results:

I hope this is along the lines of what you're looking for!

Answer 2

Thanks for your answers.. Done that using this script

# 1.a   Checking Polygon is Touching or not
                    polys = []  
                    selected_polygon = []
                    rowcount = 0  
                    with arcpy.da.SearchCursor("Census_data","Shape@") as cursor:
                            for row in cursor:
                                polys.append(row[0])
                                rowcount = rowcount + 1
                    if(rowcount >= 1):
                            with arcpy.da.SearchCursor("Census_data","Shape@") as cursor:
                                for row in cursor:  
                                    selected_polygon.append(row[0])

                            for i in range(len(selected_polygon)):  
                                overlap = 0  
                                for j in range(len(polys)):  
                                    if selected_polygon[i].distanceTo(polys[j]) == 0:  
                                        overlap = overlap + 1  
                                if overlap >= 1:  
                                    print ("Touching")

                                else:
                                    print ("Not Touching")
                                    break